|
(11) | EP 0 697 838 B1 |
| (12) | EUROPEAN PATENT SPECIFICATION |
|
|
| (54) |
TROCAR TROKAR TROCART |
|
|
|||||||||||||||||||||||||||||||
| Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention). |
[0001] The present invention is directed to trocars for inserting an access tube through an abdominal wall, and more particularly to a trocar having a retractable obturator.
[0002] A large number of abdominal surgical procedures are performed with laparoscopic techniques in order to avoid a large skin incision. Typically in laparoscopic surgery, a special needle (e.g. a needle similar to the needle described in U S Patent No. 4 808 168) is inserted through the skin, and used to inflate the abdominal cavity with an insufflating gas such as carbon dioxide (CO2). Once the abdomen is adequately dilated, the needle is removed and a rigid access tube or cannula with a diameter larger than the pneumoneedle (for example 5, 10 or 11 mm) is passed through the skin in generally the same location.
[0003] The access tube provides access for laparoscopic surgical tools such as a laparoscope, the stapler described in U S Patent No. 5 040 715 or the surgical clip appliers described in U S Patent No.'s 5 084 057 and 5 100 420. To drive the access tube through the skin, the surgeon places a trocar in the lumen of the access tube to provide a sharp leading edge for cutting tissue.
[0004] The art is replete with trocar devices, including those shown in U S Patent No's. 4 535 773, 4 601 710, 4 654 030, 4 902 280 and 4 931 042. Those trocars typically comprise an obturator with cutting surfaces for penetrating the skin, and a spring-loaded protective sleeve that surrounds the obturator. As these trocar devices are urged through the skin, friction with the skin causes the protective sleeve to slide proximally (rearwardly). After the access tube has penetrated through the skin, there is no longer friction between the protective sleeve and the skin, and the spring is designed to urge the protective sleeve distally (forwardly) to cover the cutting surfaces. Some of those trocars lock the protective sleeve in the forward position to reduce the risk of accidental puncture of the underlying organs.
[0005] These prior art trocars rely on a similar principle of operation: the friction or drag on the protective sleeve as the trocar is advanced through the skin pushes the protective sleeve back (proximally) to expose the cutting surfaces. Once the access tube has penetrated the skin, the drag on the protective sleeve is reduced and the sleeve accelerates distally (forwardly) under the bias of the spring to cover the cutting surfaces.
[0006] Those existing trocars encounter problems because a significant amount of force usually must be applied to penetrate the skin (particularly the tough fascia). As a result of the significant insertion force, the trocar may continue to advance toward the underlying organs after it has penetrated the skin. The protective sleeve must "catch up" to the moving trocar point before the trocar reaches the underlying organs. This action may be delayed if the protective sleeve is hung up on tissue.
[0007] In addition to the prior art trocars described above, several documents disclose trocars which ultimately retract the obturator relative to the cannula after the obturator has pierced the tissue of the abdominal wall. Such documents include U S Patent No. 4 525 773 to Yoon, U S Patent No. 5 116 353 to Green (and related European Patent Publication 0 479 130), U S Patent No. 5 104 382 to Brinkerhoff et al. and U S Patent No. 5 152 754 to Plyley et al. Additionally, a trocar having an obturator which ultimately retracts relative to the cannula has been on sale in this country by Origin Medsystems, Inc. prior to the filing date of the present application.
[0008] However, with the trocar sold by Origin Medsystems, Inc. and the trocars described in U S Patent No. 5 116 353 to Green (and related European Patent Publication 0 479 130), the obturator first moves distally away from the cannula (and thus toward the underlying organs) in order to actuate the mechanism which ultimately retracts the obturator relative to the cannula. This distal movement occurs just at the time when it is least desirable, that is, the distal movement of the obturator relative to the cannula occurs when the obturator pierces the tissue of the abdominal wall, clearly an undesirable result.
[0009] U S Patent No. 5 152 754 discloses a trocar comprising an obturator which retracts relative to the access tube just after the obturator pierces the tissue defining the body cavity. U S Patent No. 5 104 382 also discloses an obturator which retracts relative to a cannula. However, in each of 5 152 754 and 5 104 382, the devices include a member between the obturator and the cannula which necessarily limits the size of the obturator. For example, Brinkerhoff et al. 5 104 382 includes a shield between the obturator and cannula.
[0010] WO 93/04716 describes a retractable trocar according to the preamble of claim 1 with means to shield the obturating tip of the trocar after it has achieved its piercing function. When pressure on the trocar is released upon completion of the piercing a plate moves upward under the influence of a cam surface and an extension disengages from a shoulder to release the trocar for movement to the retracted position. At this point a further distal action of the trocar occurs just prior to retracting.
[0011] It is the object underlying the present invention to provide a trocar for facilitating insertions of a cannula through tissue defining a body cavity of a patient.
[0013] According to the present invention there is provided a trocar which (1) automatically retracts an obturator relative to a cannula after the tissue defining a body cavity has been penetrated; (2) includes a retracting means for retracting the obturator relative to the cannula after the tissue has been penetrated along a path which is at least substantially free of distal movement of the obturator relative to the cannula, and preferably completely free of distal movement of the obturator relative to the cannula; (3) preferably includes the retracting means in a proximal portion of the obturator where it is remote from cutting surfaces of the obturator where it may be adversely affected by tissue, blood, fat, etc.; (4) preferably includes a retracting means which is completely independent of the cannula; (5) is preferably free of structure (e.g. such as a trigger or protective sleeve and its attendant bias which may increase the insertion force of the trocar) between the obturator and the cannula at the distal end of the cannula to afford a smooth transition between the obturator and the cannula at the distal end of the cannula, and to eliminate the chance that such structure (e.g. the trigger or protective sleeve) may damage or traumatize tissue; (6) is preferably free of structure between the cannula and the obturator at the distal end of the cannula so that the size of the obturator for use with a given size cannula may be maximized, and conversely, so that the size of the cannula for use with a given obturator may be minimized; and (7) which uses mechanical force or pressure sensing means to sense when the tissue defining the body cavity has been penetrated so that the trocar does not rely upon any electronic components which introduce response times and the potential for electronic failure which may prevent the proper operation of the trocar.
[0014] According to the present invention, there is provided a trocar for facilitating insertion of a cannula through tissue defining a body cavity, such as the abdominal wall of a patient. The trocar comprises a housing, and an obturator extending from the housing.
[0015] The obturator comprises a shaft for placement in a lumen of the cannula, and cutting surfaces for cutting the tissue. The obturator is mounted for movement between a tissue cutting position with the cutting surfaces projecting beyond a distal end of the cannula, and a retracted position with the cutting retracted within the distal end of the cannula.
[0016] The obturator is elongate and has a longitudinal axis defining axial and radial directions and angular displacements. Preferably the obturator comprises a proximal portion having a pin, and a distal portion having the cutting surfaces. The pin is mounted for angular movement relative to the distal portion of the obturator between an armed position and a release position that is angularly spaced from the armed position relative to the longitudinal axis. The trocar also includes a retracting means for biasing the obturator from the tissue cutting position toward the retracted position.
[0017] Additionally, the trocar includes a clutch for retaining the obturator in the tissue cutting position against the bias of the retracting means while the tissue is being cut, and for automatically releasing the obturator to allow the retracting means to retract the obturator from the tissue cutting position toward the retracted position after the trocar has at least partially penetrated the tissue. Alternatively, the clutch may be described as a latching and mechanical sensing and releasing means.
[0018] The clutch affords movement of the obturator from the tissue cutting position toward the retracted position along a path that is substantially free of distal movement of the obturator relative to the cannula. More preferably, the path of the obturator after the tissue has been at least partially penetrated is completely free of distal movement of the obturator relative to the cannula.
[0019] The retracting means retracts the obturator from the tissue cutting position to the retracted position after the pin moves about the longitudinal axis from the armed position toward the release position. The retracting means comprises an axial biasing means for axially biasing the obturator from the tissue cutting position toward the retracted position, and angular biasing means for biasing the pin toward the release position. Preferably the retracting means comprises a coil spring that provides a torque for angularly moving the pin from the armed toward the release position, and that provides an axial force for moving the obturator toward the retracted position.
[0020] The clutch preferably comprises the proximal portion of the obturator having a first, friction clutch surface, and the distal portion of the obturator having a second, friction clutch surface. When the obturator is pressed against the tissue, the second, friction clutch surface frictionally engages the first, friction clutch surface and contributes to a first resistance to angular movement about the longitudinal axis between the proximal and distal portions of the obturator from the armed toward the release position. When the tissue has been at least partially penetrated by the obturator, resistance to angular (e.g. rotational) movement between the proximal and distal portions of the obturator about the longitudinal axis is less than the torque, and the proximal portion of the obturator is allowed to rotate from the armed position toward the release position.
[0021] The trocar housing has guide surfaces including a ledge surface that abuts the pin to retain the pin in the armed position prior to the obturator being advanced against the tissue. Preferably, the clutch comprises an arming ring having a shoulder surface that abuts the pin as the obturator is advanced through the tissue to restrict movement of the obturator from the tissue cutting position to the retracted position, and surfaces defining an aperture which are angularly spaced from the shoulder surface and which allow the pin to pass when the obturator moves from the tissue cutting position toward the retracted position.
[0022] The arming ring is mounted for axial movement between a distal position and a proximal position. The clutch also preferably comprises arming ring biasing means for providing an arming ring biasing force for biasing the arming ring distally, and retaining means for releasably retaining the arming ring in the proximal position against the bias of the arming ring biasing means. Prior to pressing the obturator against the tissue, the arming ring biasing means biases the obturator distally through abutment between the pin and the shoulder surface of the arming ring, and the abutment between the shoulder surface of the arming ring and the pin resists movement of the obturator to the retracted position. As the obturator is pressed against the tissue, the arming ring moves from the distal position toward the proximal position where the retaining means engages the arming ring to retain the arming ring in the proximal position.
[0023] The present invention will be further described with reference to the accompanying drawing wherein like reference numerals refer to like parts in the several views, and wherein:
Figure 1 is an exploded view of portions of a trocar according to the present invention and a portion of a cannula for use with the trocar;
Figure 2 is a perspective view of a trocar according to the present invention assembled in a cannula with portions broken away or omitted to illustrate details;
Figure 3A through 6C sequentially illustrate the operation of a trocar according to the present invention wherein:
Figures 3A, 3B and 3C illustrate the approximate positions of elements of a trocar according to the present invention with the obturator in a retracted position relative to the cannula; wherein:
Figure 3A is a perspective view of some of the elements of the trocar according to the present invention, illustrating the position of the elements when the obturator is in a retracted position;
Figure 3B is a partial side view of the trocar according to the present invention and a portion of a cannula with portions of each omitted to illustrate details, and which illustrates the obturator retracted within the distal end portion of the cannula;
Figure 3C is a perspective view of portions of the trocar according to the present invention and a cannula with portions of each broken away or omitted to illustrate details, which illustrates many of the elements of the trocar shown in Figure 3A but which shows a different cutting surface;
Figures 4A, 4B and 4C illustrate the approximate positions of elements of a trocar according to the present invention with an obturator in a distalmost position relative to the cannula, such as occurs when a user is pressing on a button member of the present invention after the button member is moved to its distal limit; wherein:
Figure 4A is a perspective view of some of the elements of the trocar according to the present invention, illustrating the position of the elements when the obturator is in a distalmost position;
Figure 4B is a partial side view of the trocar according to the present invention and a portion of a cannula with portions of each omitted to illustrate details, and which illustrates the obturator in a distalmost position relative to the cannula;
Figure 4C is a perspective view of portions of the trocar according to the present invention and a cannula with portions of each broken away or omitted to illustrate details, which illustrates many of the elements of the trocar shown in Figure 4A but which shows a different shaped cutting surface;
Figures 5A and 5B illustrate the approximate positions of elements of a trocar according to the present invention with an obturator in an "armed" position that is spaced slightly proximally relative to the cannula from its position shown in Figures 4B and 4C, such as occurs when a user releases pressure on the button member after the button member is moved to the position shown in Figures 4A, 4B and 4C, but prior to cutting tissue; wherein:
Figure 5A is a perspective view of some of the elements of the trocar according to the present invention, illustrating the position of the elements when the obturator in the armed position;
Figure 5B is a partial side view of the trocar according to the present invention and a portion of a cannula with portions of each omitted to illustrate details, and which illustrates the obturator in a position that is spaced slightly proximally relative to the cannula than its position shown in Figure 4B;
Figures 6A, 6B and 6C illustrate the approximate positions of elements of a trocar according to the present invention with an obturator in an "tissue cutting" or extended position that is spaced slightly proximally relative to the cannula from its position shown in Figure 5B, such as occurs when a user presses the obturator against tissue, but prior to complete penetration of the tissue; wherein:
Figure 6A is a perspective view of some of the elements of the trocar according to the present invention, illustrating the position of the elements when the obturator is in a tissue cutting position;
Figure 6B is a partial side view of the trocar according to the present invention and a portion of a cannula with portions of each omitted to illustrate details, and which illustrates the obturator in a tissue cutting position;
Figure 6C is a perspective view of portions of the trocar according to the present invention and a cannula with portions of each broken away or omitted to illustrate details, which illustrates many of the elements of the trocar shown in Figure 6A but which shows a different shaped cutting surface;
Figures 7A through 7F are perspective, partially schematic views of portions of a trocar according to the present invention which sequentially illustrate movement of some of the elements of the trocar during use of the trocar; wherein:
Figures 7A, 7B, 7C and 7D sequentially show the approximate positions of some of the elements of the trocar as the obturator is moved from its position shown in Figure 3B to its position shown in Figure 4B;
Figure 7E shows the approximate position of some of the elements of the trocar when the obturator is in the position shown in Figure 5B;
Figure 7F shows the approximate position of some of the elements of the trocar when the obturator is in the position shown in Figure 6B;
Figure 8 is a perspective view of elements of a trocar according to the present invention which sequentially illustrates the position of a pin of the trocar just after the tissue is penetrated and as the trocar retracts from the position shown in Figures 6A through 6C toward the position shown in Figures 3A through 3C with dashed lines, and which illustrates one example of a path that the pin may follow;
Figure 9 is a perspective view of portions of an obturator for use in the trocar according to the present invention; with portions broken away to illustrate details;
Figure 10 is perspective view of a portion of a housing for use in a trocar according to the present invention;
Figure 11 is a perspective view illustrating a second species of clutch surfaces for use in the trocar according to the present invention, which favors rotation of a proximal portion of the obturator relative to a distal portion in one direction; and
Figure 12 is a sectional view of proximal and distal portions of a trocar having a third species of clutch surfaces, which illustrates frusto-conically shaped clutch surfaces.
[0024] Referring now to Figures 1 through 10 of the drawing there is shown an embodiment of a trocar device or assembly generally designated by reference character 10. The trocar 10 is adapted to be placed in a cannula 20 to facilitate the insertion of the cannula 20 through tissue 9 defining a body cavity (see Figure 2). For example, the tissue 9 may comprise the abdominal wall of a patient and the body cavity may comprise the abdominal cavity of a patient.
[0025] The cannula 20 may include an access tube 21 having a lumen 24 terminating in a distal end 22. The cannula 20 is preferably used during laparoscopic surgery and has a large, generally funnel-shaped fixture 26 at its proximal end. The access tube 21 provides an entryway for instruments used in surgery such as laparoscopes, staplers and clip appliers. Examples of such surgical instruments are described in U S Patent No.'s 5 040 715, 5 084 057, 5 100 420, 5 171 247, 5 171 249 and 5 176 695.
[0026] The cannula 20 may include means for supplying pressurized gas to the abdomen such as a stopcock valve 23. The stopcock valve 23 is a means by which pressurized fluid (insufflating gas) can be provided to the lumen 24 to maintain gas pressure in the body cavity, and thereby keep the cavity inflated to facilitate the surgical procedure.
[0027] The cannula 20 may also include a means such as a trap door valve (not shown) generally adjacent the proximal end of the cannula 20 to restrict the escape of fluid through the cannula when it is not occluded by the trocar or surgical instrument. For example, the trap door may comprise a trap door similar to the trap door shown in U S Patent No. 5 152 754. Alternatively, the trap door valve may be replaced with a slotted elastomeric valve similar to the valve shown in U S Patent No. 4 177 814. Other alternatives may also be utilized to retain pressure within the abdominal cavity when the surgical tool or trocar is removed from the cannula 20, such as an iris-like valve.
[0028] The trocar 10 comprises a housing or handle 28 and an elongate obturator 30 extending from the housing 28. The handle 28 is generally rounded to conform to the palm of a user. The handle 28 is adapted to be received in an upper or proximal portion of the cannula 20 which restricts movement of the cannula 20 relative to the housing 28 (see Figure 2).
[0029] The direction of elongation of the obturator 30 and its center define an imaginary, longitudinal axis A (and thus axial directions), and also radial direction R (Figure 2). Angular displacements may also be measured relative to the axis A of the trocar.
[0030] The obturator 30 comprises a proximal portion 31 having a locking pin 32, and a distal portion having a shaft 34 for placement in the lumen 24 of the cannula 20, pin slot surfaces 36 for receiving the pin 32, and cutting surfaces 35 for cutting the tissue 9.
[0031] The cutting surfaces 35 may comprise any suitable geometry and are illustrated in Figures 2 and 3B, 4B, 5B and 6B as a generally conical shape terminating in a sharp point, and in Figures 3C, 4C and 6C as the intersections of three generally planar surfaces. However, any suitable cutting surfaces may be used, including a hollow structure with cutting surfaces on its periphery.
[0032] The trocar 10 of the present invention preferably includes an obturator 30 having surfaces (e.g. 39) adapted to abut at least the distal end of the cannula lumen 24. Preferably, the trocar 10 is free of structure between the obturator 30 and the cannula 20 at the distal end of the cannula 20 when the trocar is placed in the cannula. Note Figure 2 which illustrates surfaces 39 of the trocar 10 which abut the distal end of the cannula lumen 24. A trocar that is free of structure between the obturator 30 and the cannula 20 at the distal end of the cannula 20 affords the maximum size of an obturator (and its associated cutting surfaces) for a given size of cannula lumen 24. Additionally, such a trocar is believed to exhibit a beneficial profile for ease of insertion of the trocar/cannula assembly.
[0033] Alternatively, but not preferably, the trocar 10 may include a thin, generally cylindrical member (not shown) that is coaxially mounted about the obturator 30 and which extends from the housing 28 a length, such that, when the trocar 10 is assembled in the cannula 20, the distal end of the thin, cylindrical member generally abuts or is spaced slightly proximally or distally from the distal end 22 of the cannula. Preferably, the thickness of the walls of the thin, cylindrical member is minimized (e.g. less than about 0.1 to about 0.3 millimeters). The thin, cylindrical member is rigidly attached to the housing 28 so that it does not move relative to the housing 28 or cannula 20 as the cannula is inserted into the abdominal cavity. In this embodiment, when the obturator 30 is in the position shown in Figure 2 and the trocar 10 is subsequently withdrawn from the cannula 20, the obturator 30 will be situated within the thin, cylindrical member (e.g. the thin cylindrical member will extend distally beyond the cutting surfaces of the obturator). The end of the thin, cylindrical member assists in protecting a user's digits from coming into contact with the sharp obturator after the trocar 10 is removed from the cannula 20.
[0034] The trocar 10 preferably includes a means for restricting rotation or angular displacement of the distal portion of the obturator relative to the housing 28 (and thus the cannula 20). As best seen in Figures 1 and 10, that means may comprise key surfaces 37 on the shaft 34 that are adapted to abut key way guide surfaces 38 formed on a portion of the housing 28. Abutment between the key surfaces 37 and the key way guide surfaces 38 prevents rotation of the shaft 34 of the obturator (the distal portion of the obturator) relative to the housing 28 (and thus the cannula 20), but allows the shaft 34 to move axially relative to the housing 28 when the obturator retracts or extends.
[0035] The trocar 10 also preferably includes a means mounting the pin 32 for angular movement relative to the distal portion of the obturator between an armed position (Figures 4A, 4B, 4C, 5A, 5B, 6A, 6B and 6C) and a release position (Figures 3A, 3B and 3C) that is angularly spaced from the armed position. That means may include the pin slot surfaces 36. Although the position of the pin 32 in Figure 6A is axially spaced from the position of the pin 32 in Figure 4A, as used in this application, the position of the pin 32 in both Figures 4A and 6A is referred to herein as being in the "armed" position as, in each Figure, the pin 32 is in generally the same angular position relative to the longitudinal axis A.
[0036] As best seen in Figure 9, when the trocar 30 is assembled, the pin 32 of the proximal portion 31 is received in the pin slot surfaces 36 of the distal portion of the obturator to allow the proximal portion of the obturator to rotate relative to the distal portion of the obturator. The pin slot surfaces 36 should be slightly wider than the diameter of the pin 32 to afford movement of the pin 32 between the armed and release positions.
[0037] The trocar 10 also preferably includes a button 48 associated with the obturator 30 that has surfaces adapted to be pressed by a user's digit (e.g. the user's thumb or finger). The button 48 is mounted to the proximal portion 31 of the obturator so that it can rotate relative to the proximal portion 31 of the obturator. For example, the undersurface of the button 48 may include an axially projecting shaft (not shown) that is adapted to be snap fit into a hole (see Figure 1) in the proximal portion 31 of the obturator.
[0038] The trocar 10 includes a means mounting the obturator 30 for axial movement relative to the cannula 20 (and the housing 28 as well). That means may comprise an obturator sleeve or guide 40 mounted to the housing 28 so that the sleeve 40 does not move relative to the housing 28 (or cannula 20 when the trocar is inserted in the cannula). The guide 40 has guide surfaces adapted to abut the pin 32 of the proximal portion 31 of the obturator. The guide surfaces include proximal 41 and distal 42 end surfaces, ledge surfaces 43 and ramp or spiral surfaces 44.
[0039] When the pin 32 abuts the proximal end surface 41, the obturator 30 is in a retracted or proximalmost position relative to the cannula 20 (or the housing 28), and when the pin 32 abuts the distal end surface 42, the obturator is in a distalmost position relative to the cannula 20 (or housing 28). As explained in greater detail below, when the pin 32 abuts the ledge surface 43 and is in the position shown in Figures 5A and 5B, the obturator 30 is in an armed position, and when the pin 32 is in the position relative to the sleeve 40 shown in Figures 6A, 6B and 6C, the obturator 30 is in a tissue cutting position.
[0040] The trocar 10 also includes a retracting means for biasing the obturator 30 from the tissue cutting position (Figure 6A, 6B and 6C) toward the retracted position (Figures 3A, 3B and 3C). The retracting means preferably comprises axial biasing means for axially biasing the obturator 30 from the tissue cutting position toward the retracted position, and angular biasing means for biasing the pin 32 from the armed (Figures 4A-4C, 5A-5B and 6A-6C) toward the release position (Figures 3A-3C).
[0041] The angular biasing means provides a torque Tr about the axis A for moving the pin 32 from the armed toward the release position, and the axial biasing means provides an axial force (Fr) for moving the obturator 30 toward the retracted position. For example, the retracting means may comprise a torsion and compression coil spring 50 adapted to be coaxially mounted about the proximal portion 31 of the obturator. The spring 50 is in compression and also provides a torque about the axis A on the proximal portion 31 of the obturator in the direction T shown in Figures 1 and 2.
[0042] The spring 50 has a pair of ends. One of the spring's ends is operatively connected to (or abuts) a stud 51 which is attached to the sleeve 40 of the housing 28 and the other is operatively connected to a stud 52 on the proximal portion 31 of the obturator 30. While the retracting means has been illustrated as a single, coil spring 50, it should be noted that the retracting means may comprise any suitable type or number of springs so long as an angular and axial component of force are provided. For example, a pair of springs may be used comprising a leaf spring and a torsion spring. Other examples of suitable biasing means include compressed resilient members, gas/fluid springs and magnets.
[0043] The trocar 10 includes a clutch for retaining the obturator 30 in the tissue cutting position (Figures 6A through 6C) against the bias of the retracting means (e.g. spring 50) while the tissue 9 is being cut, and for releasing the obturator 30 to allow the retracting means to retract the obturator 30 from the tissue cutting position toward the retracted position (Figures 3A through 3C) after the trocar 10 has cut the tissue 9 sufficiently to afford passage of the cannula 20 into the abdominal cavity. Alternatively, the clutch may be described as a latching and mechanical sensing and releasing means.
[0044] The clutch comprises the proximal portion 31 of the obturator having a first, friction clutch surface 12, and the distal portion of the obturator 30 having a second, friction clutch surface 14. Since the keyway guide 38 holds the shaft 34 rotationally fixed relative to the housing 28 and cannula 20, the surface 12 may be referred to as a stationary clutch surface, and the surface 14 may be referred to as a movable clutch surface.
[0045] The resistance to rotation about the axis A provided by the first and second clutch surfaces 12 and 14 as the trocar is being inserted in the tissue 9 (see Figure 6B) should be sufficient to overcome the torque T provided by spring 50. The resistance to rotation provided by the clutch will depend on numerous factors including, the friction coefficients of the first and second clutch surfaces 12 and 14, the size and shapes of the clutch surfaces, the minimum axial insertion force on the obturator (and thus the surfaces 12 and 14) and the tolerances and friction coefficients of the various components of the clutch (including those described below). The clutch should be designed to prevent rotation of the pin 32 from the armed toward the release position until the tissue 9 has been at least partially penetrated.
[0046] While the clutch surfaces 12, 14 have been illustrated as generally circular, planar surfaces, it should be noted that the clutch surfaces may comprise any suitable shape, so long as the clutch surfaces afford angular (preferably rotational) movement of the proximal portion 31 of the obturator relative to the distal portion of the obturator 30. Figure 12 illustrates a substantially frusto-conical clutch surface 12B. Other examples include a substantially conical shaped clutch surface, or any other surfaces that are symmetrical about the axis A. Figure 11 illustrates a clutch surface 12A which favors rotation of the clutch surfaces in one direction relative to the axis A over the other. This may be beneficial in assisting the user in arming the trocar.
[0047] Since the clutch temporarily retains the obturator 30 in the tissue cutting position against the bias of spring 50, the clutch also preferably comprises an arming ring 56 having shoulder surfaces 57 adapted to abut the pin 32 as the obturator is advanced through the tissue 9 (Figure 6A). The shoulder surfaces 57 restrict movement of the obturator 30 from each of the distalmost, armed and tissue cutting positions toward the retracted position. The arming ring 56 also includes surfaces defining an aperture 58 which are angularly spaced (relative to the axis A) from the shoulder surfaces 57 and which allow the pin 32 to pass when the obturator 30 moves between the retracted and distalmost positions.
[0048] A means such as arming ring stops 54 on the sleeve 40 mount the arming ring 56 for axial movement between a distal position (Figures 4A, 4B, 4C, 5A and 5B) and a proximal position (3A, 3B, 3C, 6A, 6B, 6C). The clutch also preferably includes an arming ring biasing means such as generally U-shaped springs 53 for providing an arming ring biasing force (Fa) that axially biases the arming ring 56 distally. Preferably, the arming ring biasing force (Fa) is at least ten times greater than the axial force (Fr) provided by the spring 50 to assist in preventing the premature firing of the trocar 10.
[0049] The U-shaped springs each have a pair of ends, one of which is operatively associated (e.g. attached) with the arming ring 56 and the other being operatively associated with the housing 28 (through engagement with base portions of the sleeve 40). Additionally, the clutch preferably comprises retaining means, such as leaf spring retainers for releasably retaining the arming ring 56 in the proximal position against the bias of U-shaped springs 53. The leaf spring retainers are movable relative to the housing 28 and arming ring 56 between an engaged position (Figures 3A, 3B, 3C, 6A, 6B, 6C) where engagement surfaces 61 engage the arming ring 56 to hold the arming ring 56 in the proximal position against the bias of springs 53, and a disengaged position (Figures 4A, 4B, 4C, 5A and 5B) which is spaced from the engaged position and allows the arming ring 56 to move toward the distal position.
[0050] The leaf spring retainers have a leaf spring 62 which is adapted to abut a portion of the housing 28 to bias the leaf spring retainer toward the engaged position, and cam follower surfaces 63 that are adapted to engage cam surfaces 33 on the pin 32 to move the leaf spring retainers from the engaged toward the disengaged position. This action is described in greater detail below.
[0051] The leaf spring retainers may comprise any suitable shape such as the shape shown in Figures 3A through 6C. Alternative, the leaf spring retainers may comprise the shape shown in Figures 7A through 7F, or any suitable shape or combination of springs and other elements. For example, the retaining means may comprise a torsion spring with a cam follower surface for cooperating with the shape of the cam surface on pin 32, and a retaining or engagement surface.
[0052] Any suitable materials may be used to construct the elements of the trocar and cannula according to the present invention. For example, medical grade plastics and metals may be used.
OPERATION
[0053] The operation of the trocar 10 will now be described with reference to Figures 1 through 10, and particularly to Figures 3A through 6C. Typically, the trocar will be transported in a transportation package in an assembled position, that is, the trocar 10 will be inserted into the lumen 24 of the cannula 20 with the elements of the trocar and cannula generally in the position shown in Figures 2 and 3A through 3C. Next, the trocar will be removed from the transportation package. In that position, the obturator 30 is in a retracted position and the cutting surfaces 35 are retracted within the distal end 22 of the cannula 20 so that sensitive or vulnerable items (such as the fingers D of medical personnel) are somewhat protected from contact with the sharp cutting surfaces 35.
[0054] Also, in the retracted position, the U-shaped springs 53 do not bias the obturator 30 distally. The engagement surfaces 61 of the leaf spring retainers engage the arming ring 56 and retain the ring 56 in the proximal position.
[0055] To initially prepare the trocar 10 to cut tissue in a laparoscopic procedure, a user may manually press (e.g. with the user's digit D) the button 48 distally relative to the housing 28 (and cannula 20). Figures 4A-4C illustrate the positions of some of the elements of the trocar 10 while a user is pressing on the button 48 and after the button 48 is moved to its distal limit.
[0056] Figures 7A-7D sequentially illustrate one example of the path that the pin 32 may follow when the pin moves from the position generally shown in Figures 3A-3C to the position shown in Figures 4A-4C. The pin 32 moves along the ramp surfaces 44 and through the aperture 58 of the arming ring 56. During that movement, engagement between the pin 32 and the ramp surfaces 44 of the sleeve 40 cause the pin 32 to be moved (cammed) angularly relative to the axis A from the release (Figure 3A) toward to the armed (Figure 4A) position. Also during that movement, the pin 32 is allowed to pass from a position spaced proximally relative to the arming ring 56 to a position spaced distally as the pin 32 passes through aperture 58 in the arming ring 56. Just after the pin 32 passes through aperture 58, the cam surfaces 33 on the pin 32 engage the cam follower surfaces 63 on the leaf spring retainers and move the leaf spring retainers from the engagement position to the disengaged position (Figure 4A) thereby allowing the arming ring 56 to move from the proximal position to the distal position under the bias of U-shaped springs 53.
[0057] When a user releases pressure on the button member 48 after the button member 48 is moved to the position shown in Figures 4A, 4B and 4C, but prior to cutting tissue 9, the obturator 30 retracts slightly from the position shown in Figures 4A, 4B and 4C to the position shown in Figures 5A and 5B. The obturator 30 retracts due to the axial biasing force provided by spring 50, until it becomes operatively associated with the ring 56 and the bias provided by the U-shaped spring members 53.
[0058] Preferably, the axial biasing force provided by the spring 50 is less than the axial component of the arming ring biasing force provide by the U-shaped spring members 53. The arming ring 56 will remain in the distal position and the pin 32 will slightly retract due to the spring 50 until it contacts the shoulder 57 of the arming ring 56. Since the axial force provided by the spring members 53 is greater than the axial biasing force on the pin 32 provided by the spring 50, the pin 32 will not retract beyond the position shown in Figure 5A.
[0059] This relationship may be described by the following equation:
wherein:
Fi = the minimum axial insertion force on the obturator 30 as the obturator is advanced through the tissue 9;
Fa = the axial force on the obturator 30 provided by the arming ring biasing force (e.g. provided by the springs 53) which biases the obturator 30 distally; and
Fr = the axial force on the obturator provided by the axial biasing means (e.g. provided by the spring 50) which biases the obturator 30 proximally. Preferably, Fa > 10 times Fr , as a safety factor to restrict the chances that the obturator 30 will prematurely retract.
[0060] In the position shown in Figure 5A, the pin 32 abuts the ledge surface 43 of the sleeve 40 (also see Figure 7E). Abutment between the pin 32 and the ledge 43 blocks the pin 32 from rotating from the armed position toward the release position under the bias of the angular biasing means (the torque about axis A provided by the spring 50). The trocar 10 is now ready to be pressed against tissue 9.
[0061] Prior to the time the obturator 30 is pressed against the tissue 9, the U-shaped springs 53 bias the obturator 30 distally through abutment between the pin 32 and the shoulder surface 57 of the arming ring 56. The abutment between the shoulder surface 57 and the pin 32 resists movement of the obturator 30 toward the retracted position.
[0062] As the obturator 30 is pressed against the tissue 9, but prior to the complete penetration of the tissue 9, the elements of the trocar 10 will be in approximately the positions shown in Figures 6A through 6C. As the obturator 30 is initially pressed against the tissue 9, the arming ring 56 moves from the distal toward the proximal position where the engagement surfaces 61 of the leaf spring retainers engages the arming ring 56.
[0063] The obturator 30 is illustrated in the tissue cutting position in Figures 6A though 6C, and Figure 7F. In the tissue cutting position, at least some of the cutting surfaces 35 of the obturator 30 project beyond the distal end 22 of the cannula 20.
[0064] As shown in Figure 6A, as the obturator 30 is pressed through the tissue 9, the pin 32 is moved proximally off ledge surface 43 so that the ledge surface 43 no longer prevents the proximal portion 31 of the obturator 30 from rotating about the axis A relative to the distal portion of the obturator 30. However, when the obturator 30 is pressed against the tissue 9, the second, friction clutch surface 14 frictionally engages the first, friction clutch surface 12 and provides a first resistance to angular (e.g. rotational) movement between the proximal 31 and distal portions of the obturator 30 from the armed toward the release position. This first resistance to angular motion between the proximal 31 and distal portions of the obturator is greater than the torque about the axis A provided by the spring 50. Thus, as the trocar is being initially pressed against the tissue 9, the obturator 30 will not retract because the pin 32 will still abut the shoulder surface 57 of the ring 56.
[0065] When the tissue 9 is at least partially penetrated (preferably completely penetrated) or when the distal end 22 of the cannula 20 is generally adjacent the body cavity, the clutch automatically releases the obturator 30 to allow the spring 50 to retract the obturator 30 from the tissue cutting position toward the retracted position. When the tissue 9 is penetrated, the resistance to angular (e.g. rotational) movement between the proximal 31 and distal portions of the obturator 30 is less than the torque provided by the spring 50, due to the absence or reduction of drag-on the obturator 30 (and the attendant reduction in the force that presses the clutch surfaces 12 and 14 together) that was previously provided by engagement with the tissue 9. Thus, the proximal portion 31 of the obturator 30 rotates from the armed toward the release position.
[0066] After the pin 32 rotates about axis A from the armed toward the release position, the pin 32 will clear the shoulder surface 57 of the arming ring 56, and the retracting means (spring 50) may then retract the obturator 30 from the tissue cutting position (see Figure 7F) to the retracted position (see Figure 7A).
[0067] Figure 8 illustrates elements of the trocar 10 and four discrete positions of the pin 32 as it moves along one example of a path P from the armed toward the release position. As shown in Figure 8, the path P is the path of the axis of the pin 32 as it moves from the armed position toward the release position. Preferably, the clutch affords movement of the obturator 30 from the tissue cutting position toward the retracted position along a path P that is completely free of distal movement of the obturator 30 relative to the cannula 20. However, the phrase "substantially free" is used herein as a recognition that when the clutch surfaces 12 and 14 initially begin to rotate relative to each other, there may be a slight, almost negligible distal movement of the obturator 30 relative to the cannula 20 which would depend on a number of factors including the spring constant of the spring 50 and the types of surfaces used for the friction clutch surfaces 12, 14. Preferably, there is no such distal movement of the obturator 30 relative to the cannula 20, and, in the event that there is any, it should be less than about 0.5 millimeters and more preferably less than about 0.2 millimeters. However, it is believed that it is possible to construct the friction clutch surfaces 12, 14 such that there is no distal movement of the obturator 30 relative to the cannula 20 as the obturator 30 penetrates into the body cavity.
[0068] The present invention has now been described with reference to several embodiments thereof. It will be apparent to those skilled in the art that many changes or additions can be made in the embodiments described without departing from the scope of the present invention. For example, optionally, but not preferably, the clutch and retracting means may be located in a distal portion of the obturator.
a handle (28),
an obturator (30) having a proximal portion (31) and a distal portion with a cutting surface (35) for piercing the wall of the body cavity, and an axis (A), said trocar being charaterized by:
means (36) mounting said proximal and distal portions for relative angular movement about the axis of the obturator, means (50) for retracting said obturator proximally and substantially free of distal movement relative to the cannula from a tissue cutting position to a retracted position as the proximal and distal portions move angularly relative to each other after the cutting surface has at least partially penetrated through the wall of the body cavity.
a clutch (12, 14) for retaining the obturator (30) in the tissue cutting position against the bias of said retracting means (50) while the tissue is being cut, and for releasing the obturator (30) to allow the retracting means (50) to retract the obturator (30) from the tissue cutting position toward the retracted position after the trocar (10) has at least partially penetrated the tissue.
latch means for releasably holding the obturator (30) in the tissue cutting position against the bias of said biasing means, and
mechanical sensing and releasing means for sensing when the tissue defining the body cavity has been penetrated and for releasing the latch means to allow the retracting means (50) to retract the obturator (30) from the tissue cutting position to the retracted position after the tissue defining the body cavity has been at least partially penetrated.
the proximal portion (31) of the obturator rotates relative to the distal portion
after the cutting surface (35) penetrates through the tissue defining the body cavity,
and
wherein the obturator (30) retracts proximally upon the rotation of the proximal
portion (31) relative to the distal portion of the obturator (30).
said obturator (30) is elongate and has a longitudinal axis defining axial and radial directions and angular displacements,
said obturator (30) comprises a proximal portion (31) having a pin (32), and a distal
portion,
wherein said trocar (10) includes means (36) mounting said pin (32) for angular
movement relative to said distal portion of said obturator (30) between an armed position
relative to the longitudinal axis and a release position that is angularly spaced
from said armed position, and
wherein said retracting means (50) retracts the obturator (30) from the tissue
cutting position to the retracted position after the pin (32) moves from the armed
position toward the release position.
said retracting means (50) comprises axial biasing means for axially biasing said obturator (30) from said tissue cutting position toward said retracted position, and angular biasing means for biasing said pin (32) toward said release position.
said angular biasing means provides a torque for angularly moving the pin (32) about the longitudinal axis from the armed toward the release position, and
said axial biasing means provides an axial force for moving the obturator (30) toward the retracted position.
said clutch comprises said proximal portion (31) of said obturator having a first
friction clutch surface (14), and said distal portion of said obturator having a second
friction clutch surface (12),
wherein when said obturator (30) is pressed against the tissue, said second, friction
clutch surface (12) frictionally engages the first, friction clutch surface (14) and
contributes to a first resistance to angular movement between said proximal and distal
portions of said obturator (30) form said armed toward said release position, and
wherein when the tissue has been at least partially penetrated by said obturator
(30), resistance to angular movement between said proximal and distal portions of
said obturator (30) is less than said torque and the proximal portion (31) of said
obturator (30) is allowed to move angularly from said armed toward said release position.
said clutch comprises an arming ring (56) having a shoulder surface (57) adapted to abut the pin (32) as the obturator (30) is advanced through the tissue to restrict movement of the obturator (30) from the tissue cutting position to the retracted position, and surfaces defining an aperture (58) which are angularly spaced from said shoulder surface (57) and which allow the pin (32) to pass when the obturator moves from the tissue cutting position toward the retracted position.
means mounting the arming ring (56) for axial movement between a distal position and a proximal position,
arming ring biasing means (53) for providing an arming ring biasing force for biasing the arming ring (56) distally,
retaining means for releasably retaining the arming ring (56) in the proximal position
against the bias of said arming ring biasing means (53),
wherein, prior to pressing the obturator against the tissue, the arming ring biasing
means (53) biases the obturator distally through abutment between the pin (32) and
the shoulder surface (57) of the arming ring (56), and the abutment between the shoulder
surface (57) of the arming ring (56) and the pin (32) resists movement of said obturator
(30) to said retracted position, and
as the obturator (30) is pressed against the tissue, the arming ring (56) moves from said distal position toward the proximal position where the retaining means engages the arming ring (56) to retain the arming ring (56) in the proximal position.
the retracting means (50) is designed such that:
wherein:
Fi = the minimum axial insertion force on the obturator (30) as the obturator (30) is advanced through the tissue;
Fa = the axial force on the obturator (30) provided by the arming ring biasing force which biases the obturator (30) distally; and
Fr = the axial force on the obturator (30) provided by the axial biasing means which biases the obturator (30) proximally.
the retracting means (50) is preferably designed such that:
to restrict premature retraction of the obturator (30).
einen Griff (28);
einen Obturator (30), der einen proximalen Abschnitt (31) und einen distalen Abschnitt mit einer Schneidfläche (35) zum Einstechen in die Wand des Körperhohlraums und eine Achse (A) hat, wobei der Trokar gekennzeichnet ist durch:
eine Einrichtung (36), die den proximalen und distalen Abschnitt zur relativen Winkelbewegung um die Achse des Obturators anordnet, eine Einrichtung (50) zum Zurückziehen des Obturators proximal und im wesentlichen frei von distaler Bewegung relativ zur Kanüle aus einer Gewebeschneidposition in eine zurückgezogene Position, wenn sich der proximale und distale Abschnitt relativ zueinander winklig bewegen, nachdem die Schneidfläche mindestens teilweise die Wand des Körperhohlraums durchstoßen hat.
eine Kupplung (12, 14) zum Festhalten des Obturators (30) in der Gewebeschneidposition gegen die Vorspannung der Rückzugeinrichtung (50), während das Gewebe geschnitten wird, und zum Freigeben des Obturators (30), damit die Rückzugeinrichtung (50) den Obturator (30) aus der Gewebeschneidposition in die zurückgezogene Position zurückziehen kann, nachdem der Trokar (10) das Gewebe mindestens teilweise durchstoßen hat.
eine Verriegelungseinrichtung zum lösbaren Halten des Obturators (30) in der Gewebeschneidposition gegen die Vorspannung der Vorspanneinrichtung, und
eine mechanische Erfassungs- und Freigabeeinrichtung zum Erfassen, wann das den Körperhohlraum bildende Gewebe durchstoßen wurde, und zum Freigeben der Verriegelungseinrichtung, damit die Rückzugeinrichtung (50) den Obturator (30) aus der Gewebeschneidposition in die zurückgezogene Position zurückziehen kann, nachdem das den Körperhohlraum bildende Gewebe mindestens teilweise durchstoßen wurde.
der proximale Abschnitt (31) des Obturators relativ zum distalen Abschnitt dreht, nachdem die Schneidfläche (35) das den Körperhohlraum bildende Gewebe durchstößt, und wobei sich der Obturator (30) bei Drehung des proximalen Abschnitts (31) relativ zum distalen Abschnitt des Obturators (30) proximal zurückzieht.
der Obturator (30) länglich ist und eine Längsachse hat, die eine Axial- und Radialrichtung sowie Winkelverschiebungen festlegt,
der Obturator (30) einen proximalen Abschnitt (31) mit einem Stift (32) und einen
distalen Abschnitt aufweist, wobei der Trokar (10) eine Einrichtung (36) aufweist,
die den Stift (32) zur Winkelbewegung relativ zum distalen Abschnitt des Obturators
(30) zwischen einer scharfgemachten Position relativ zur Längsachse und einer Freigabeposition
anordnet, die von der scharfgemachten Position winklig beabstandet ist, und
wobei die Rückzugeinrichtung (50) den Obturator (30) aus der Gewebeschneidposition
in die zurückgezogene Position zurückzieht, nachdem sich der Stift (32) aus der scharfgemachten
Position in die Freigabeposition bewegt.
die Rückzugeinrichtung (50) eine Axialvorspanneinrichtung zum axialen Vorspannen des Obturators (30) aus der Gewebeschneidposition in die zurückgezogene Position und eine Winkelvorspanneinrichtung zum Vorspannen des Stifts (32) in die Freigabeposition aufweist.
die Winkelvorspanneinrichtung ein Drehmoment zum Winkelbewegen des Stifts (32) um die Längsachse aus der scharfgemachten in die Freigabeposition ausübt, und
die Axialvorspanneinrichtung eine Axialkraft zum Bewegen des Obturators (30) in die zurückgezogene Position ausübt.
die Kupplung den proximalen Abschnitt (31) des Obturators mit einer ersten Reibungskupplungsfläche
(14) und den distalen Abschnitt des Obturators mit einer zweiten Reibungskupplungsfläche
(12) aufweist,
wobei beim Drücken des Obturators (30) an das Gewebe die zweite Reibungskupplungsfläche
(12) einen Reibeingriff mit der ersten Reibungskupplungsfläche (14) herstellt und
zu einem ersten Widerstand gegen eine Winkelbewegung zwischen dem proximalen und distalen
Abschnitt des Obturators (30) aus der scharfgemachten in die Freigabeposition beiträgt,
und
wobei nach mindestens teilweisem Durchstoßen des Gewebes durch den Obturator (30)
ein Widerstand gegen eine Winkelbewegung zwischen dem proximalen und distalen Abschnitt
des Obturators (30) kleiner als das Drehmoment ist und sich der proximale Abschnitt
(31) des Obturators (30) aus der scharfgemachten in die Freigabeposition winklig bewegen
kann.
die Kupplung aufweist: einen Scharfschaltring (56) mit einer Schulterfläche (57), die geeignet ist, an den Stift (32) anzustoßen, wenn der Obturator (30) durch das Gewebe vorgeschoben wird, um eine Bewegung des Obturators (30) aus der Gewebeschneidposition in die zurückgezogene Position einzuschränken, sowie eine Öffnung (58) bildende Oberflächen, die von der Schulterfläche (57) winklig beabstandet sind und durch die der Stift (32) durchlaufen kann, wenn sich der Obturator aus der Gewebeschneidposition in die zurückgezogene Position bewegt.
eine Einrichtung, die den Scharfschaltring (56) zur Axialbewegung zwischen einer distalen Position und einer proximalen Position anordnet,
eine Scharfschaltring-Vorspanneinrichtung (53) zum Ausüben einer Scharfschaltring-Vorspannkraft zum distalen Vorspannen des Scharfschaltrings (56),
eine Festhalteeinrichtung zum lösbaren Festhalten des Scharfschaltrings (56) in der
proximalen Position gegen die Vorspannung der Scharfschaltring-Vorspanneinrichtung
(53),
wobei vor Drücken des Obturators an das Gewebe die Scharfschaltring-Vorspanneinrichtung
(53) den Obturator distal durch Anstoßen zwischen dem Stift (32) und der Schulterfläche
(57) des Scharfschaltrings (56) vorspannt, und das Anstoßen zwischen der Schulterfläche
(57) des Scharfschaltrings (56) und dem Stift (32) einer Bewegung des Obturators (30)
in die zurückgezogene Position widersteht, und
beim Drücken des Obturators (30) an das Gewebe sich der Scharfschaltring (56) aus der distalen Position in die proximale Position bewegt, in der die Festhalteeinrichtung in den Scharfschaltring (56) eingreift, um den Scharfschaltring (56) in der proximalen Position festzuhalten.
die Rückzugeinrichtung (50) so gestaltet ist, daß
gilt; wobei:
Fi die minimale axiale Einführkraft auf den Obturator (30) ist, wenn der Obturator (30) durch das Gewebe vorgeschoben wird;
Fa die Axialkraft auf den Obturator (30) ist, die durch die Scharfschaltring-Vorspannkraft ausgeübt wird, die den Obturator (30) distal vorspannt; und
Fr die Axialkraft auf den Obturator (30) ist, die durch die Axialvorspanneinrichtung ausgeübt wird, die den Obturator (30) proximal vorspannt.
die Rückzugeinrichtung (50) vorzugsweise so gestaltet ist, daß:
gilt, um einen verfrühten Rückzug des Obturators (30) einzuschränken.
◆ une poignée (28),
◆ un obturateur (30) ayant une portion arrière (31) et une portion avant avec une surface de coupe (35) pour percer la paroi de la cavité du corps, et un axe (A), ledit trocart étant caractérisé par :
◆ des moyens (36) d'assemblage de ladite portion arrière et de ladite portion avant pour permettre un mouvement angulaire relatif autour de l'axe de l'obturateur, des moyens (50) pour rétracter ledit obturateur vers l'arrière et substantiellement indépendamment d'un mouvement vers l'avant relatif, à la canule pour passer d'une position de coupe du tissu à une position rétractée au fur et à mesure que la portion arrière et la portion avant se déplacent angulairement l'une par rapport à l'autre après que la surface de coupe a au moins partiellement pénétré à travers la paroi de la cavité du corps.
◆ un accouplement (12, 14) pour retenir l'obturateur (30) dans la position de coupe du tissu à l'encontre de la contrainte exercée par lesdits moyens de rétraction (50) pendant la coupe du tissu, et pour déverrouiller l'obturateur (30) pour permettre aux moyens de rétraction (50) de rétracter l'obturateur (30) pour passer, depuis la position de coupe du tissu, en direction de la position rétractée après que le trocart (10) a au moins partiellement pénétré dans le tissu.
◆ des moyens mécaniques de détection et de déverrouillage pour détecter que le tissu définissant la cavité du corps a été pénétré et pour déverrouiller les moyens de verrouillage pour permettre aux moyens de rétraction (50) de rétracter l'obturateur (30) pour passer, depuis la position de coupe du tissu, à la position rétractée après que le tissu définissant la cavité du corps a été au moins partiellement pénétré.
◆ la portion arrière (31) de l'obturateur tourne par rapport à la portion avant après que la surface de coupe (35) a pénétré à travers le tissu définissant la cavité du corps, et
◆ dans lequel l'obturateur (30) se rétracte vers l'arrière lors de la rotation de la portion arrière (31) par rapport à la portion avant de l'obturateur (30).
◆ ledit obturateur (30) est de forme allongée et a un axe longitudinal définissant des directions axiale et radiale et des déplacements angulaires,
◆ ledit obturateur (30) comporte une portion arrière (31) ayant un téton (32), et une portion avant,
◆ dans lequel ledit trocart (10) inclut des moyens (36) d'assemblage du téton (32) permettant un mouvement angulaire par rapport à ladite portion avant dudit obturateur (30) entre une position armée par rapport à l'axe longitudinal et une position désarmée qui est angulairement espacée de ladite position armée, et
◆ dans lequel lesdits moyens de rétraction (50) rétractent l'obturateur (30) pour passer, depuis la position de coupe du tissu, à la position rétractée après que le téton (32) soit passé de la position armée à la position désarmée.
◆ lesdits moyens de rétraction (50) comportent des moyens de contrainte axiale pour contraindre axialement ledit obturateur (30) pour passer, depuis ladite position de coupe du tissu, vers ladite position rétractée, et des moyens de contrainte angulaire pour contraindre ledit téton (32) vers ladite position de déverrouillage.
◆ lesdits moyens de contrainte angulaire créent un couple pour faire passer angulairement le téton (32), autour de l'axe longitudinal, depuis la position armée, en direction de la position désarmée, et
◆ lesdits moyens de contrainte axiale créent une force axiale pour faire passer l'obturateur (30) vers la position rétractée.
◆ ledit accouplement comporte ladite portion arrière (31) dudit obturateur ayant une première surface d'accouplement à frottement (14) et ladite portion avant dudit obturateur ayant une seconde surface d'accouplement à frottement (12),
◆ dans lequel, lorsque l'on presse ledit obturateur (30) contre le tissu, ladite seconde surface d'accouplement à frottement (12) vient en prise, par frottement, avec ladite première surface d'accouplement par frottement (14) et contribue à une première résistance au mouvement angulaire entre ladite portion arrière et ladite portion avant dudit obturateur (30) pour passer, depuis ladite position armée, vers ladite position désarmée, et
◆ dans lequel, lorsque le tissu a été au moins partiellement pénétré par ledit obturateur (30), la résistance au mouvement angulaire entre ladite portion arrière et ladite portion avant dudit obturateur (30) est inférieure audit couple et la portion arrière (31) dudit obturateur (30) peut se mouvoir angulairement pour passer, depuis ladite position armée, vers ladite position désarmée.
◆ ledit accouplement comporte une bague d'armement (56) ayant une surface d'épaulement (57) conçue pour que le téton (32) y bute, au fur et à mesure que l'on fait avancer l'obturateur (30) à travers le tissu pour restreindre le mouvement de l'obturateur (30) pour passer, depuis la position de coupe du tissu, à la position rétractée, ainsi que des surfaces qui définissent une ouverture (58) et sont angulairement espacées de ladite surface d'épaulement (57) et permettent au téton (32) de passer lorsque l'obturateur passe, depuis la position de coupe du tissu, vers la position rétractée.
◆ des moyens d'assemblage de la bague d'armement (56) pour permettre son mouvement axial entre une position avant et une position arrière,
◆ des moyens (53) de contrainte de la bague d'armement pour créer une force de contrainte exercée sur la bague d'armement pour contraindre la bague d'armement (56) vers l'avant,
◆ des moyens de retenue pour retenir, avec possibilité de libération, la bague d'armement (56) dans la position arrière à l'encontre de la contrainte exercée par lesdits moyens (53) de contrainte de la bague d'armement,
◆ dans lequel, avant que l'on presse l'obturateur contre le tissu, les moyens (53) de contrainte de la bague d'armement contraignent l'obturateur vers l'avant par l'intermédiaire d'une butée entre le téton (32) et la surface d'épaulement (57) de la bague d'armement (56), et dans lequel le fait que le téton (32) bute contre la surface d'épaulement (57) de la bague d'armement (56) crée une résistance au mouvement dudit obturateur (30) vers ladite position rétractée et
◆ dans lequel, au fur et à mesure que l'on presse l'obturateur (30) contre le tissu, la bague d'armement (56) passe, depuis ladite position avant, vers la position arrière où les moyens de retenue viennent en prise avec la bague d'armement (56) pour retenir la bague d'armement (56) dans la position arrière.
◆ les moyens de retraction (50) sont conçus de façon que
; où
■ Fi = force minimale d'insertion axiale exercée sur l'obturateur (30) au fur et à mesure que l'obturateur (30) avance à travers le tissu;
■ Fa = force axiale, exercée sur l'obturateur (30), créée par la force de contrainte de la bague d'armement qui contraint l'obturateur (30) vers l'avant; et
■ Fr = force axiale, exercée sur l'obturateur (30), créée par les moyens de contrainte axiale qui contraignent l'obturateur (30) vers l'arrière.
◆ les moyens de retraction (50) sont de préférence conçus de façon: Fa > 10 (Fr), pour restreindre une rétraction prématurée de l'obturateur (30).